Belle and Sebastian and the Decemberists return from hiatuses with contrasting results

Longevity is a precarious aspiration in the music industry these days.

Labels don’t nurture bands like they once did. Attention spans are shorter, diverted by the wealth of other distractions and alternatives. Relevance is vital to longevity, and when a band goes four or five years between album releases, it risks squandering its relevance — the equity it accumulated from previous albums and the accompanying tours.

Two bands releasing albums this week are returning from hiatuses: Scotland’s Belle and Sebastian, who, after an absence of nearly five years, are back with “Girls in Peacetime Want to Dance,” and the Decemberists, of Portland, Ore., who just released “What a Terrible World, What a Beautiful World,” their first album in four years.

The opening track to “Terrible World” is a folk hymn from the band to its fans. “We know we belong to you,” Colin Meloy, lead vocalist and songwriter, sings plaintively. “We know you built your lives around us.… We know you threw your arms around us / In the hope we wouldn’t change / But we had to change.”

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Change occurs, but it’s subtle, not the kind that signifies a band trying to rediscover its old vigor and spirit. “Terrible World” is the follow-up to 2011’s “The King Is Dead,” an album rife with melody hooks and finessed songwriting and exercises in folk-rock and country that sound like a tribute to some of R.E.M.’s best work. “Terrible World” picks up where “King” left off and adds some unexpected, at times unwieldy, twists.

“Calvary Captain” is a love song — “I’m the remedy to your heart” — with girly background vocals and the kind of bright horn flourishes that could make you think of Phil Collins’ “Sussudio.”

“Philomena” is a sweet, cheery love song with a doo-wop/1960s girl-pop feel that erupts into an orchestral anthem. “Lake Song” is a memoir set to a light-jazz vibe — piano, bass, brushed drums — and at nearly six minutes, it feels about two minutes too long.

“Terrible World” is at its best when songs don’t crack the four-minute mark. “The Wrong Year” is one of those, a tuneful folk song bathed in mandolin, accordion, acoustic guitars and layers of warm harmonies. “Carolina Low” sounds like an old Appalachian folk ballad; so does “Better Not Wake the Baby.”

“Anti-Summersong,” which comes and goes in a dozen seconds more than two minutes, has a Celtic-folk feel, like something the Elders might have written (despite the odd call-and-response that erupts toward the end).

There’s an instant appeal to much of this album, but it also sounds like a writer and a band whittling songs into pleasant shapes with smooth finishes, a lateral move, not a headlong rush into a bold adventure.

On “Girls in Peacetime Want to Dance,” Belle and Sebastian take a few side roads into new terrain. The opener, “Nobody’s Empire,” bears some traits of the band’s early work, going back to “If You’re Feeling Sinister,” released 19 years ago. Lead singer Stuart Murdoch still has a voice that gets pegged as … pick a word: fey, twee, porcelain, wispy.

But the band is going for a fuller sound throughout the album, and the evidence arrives in “Nobody’s Empire,” which starts off as a dainty piano ballad but swerves abruptly into something else, something soulful: an array of horns, background vocals, some glockenspiel and other adornments.

“Allie” feels like psychedelic pop from the late 1960s, not quite “Odessey and Oracle,” but in the distant vicinity. “The Party Line” was released as a single late last year, and it takes B&S into disco terrain, riding a guitar riff that sounds akin to the one in Daft Punk’s “Get Lucky,” then gliding into electro-pop. Sarah Martin takes lead vocals on “The Power of Three,” an exercise in Euro-pop that her lovely voice can’t rescue from its ennui.

On “The Cat With the Cream,” Murdoch returns to the sounds of “Tigermilk” and “Sinister”: a low-tempo ballad set to the throb of a kick drum, keyboards and strings and burnished by Martin’s pretty harmonies. Then comes “Enter Sylvia Plath,” which, despite what its title implies, is a glittery disco-bomb that sounds circa 1985 and the days of the Pet Shop Boys.

“The Everlasting Muse” bears the biggest surprise. It opens as a jazzy, understated indie-pop ballad, then abruptly slows and then barges into a klezmer throwdown with a hearty singalong before returning to its initial movement, this time with horns.

A gust of percussion — congas, vibes, snapped fingers — and then a horn riff opens “Perfect Couples,” a buoyant, dancey pop tune with some vocal play that recalls Madonna’s “Vogue.”

And so it goes on “Girls in Peacetime”: Murdoch and his mates taking excursions into styles and genres that bear little resemblance to the yearning, mannered pop songs that attracted a loyal following nearly two decades ago. Completists will want this recording, maybe even the extravagant, four-LP special edition.

Newcomers are advised to start at the beginning, to put what follows into context. Anyone in between should be aware that “Girls in Peacetime” portrays a band that spent its five-year hiatus stirring up new ideas and yearning for new directions.